Series V 3.89 differential

[911tr8r]

911tr8r,

What makes you think that gears for a Bobcat, Capri or Mustang II will fit in a Series Alpine rear axle housing?

pretty sure i read it on this forum someplace

 

[911tr8r]

911tr8r,

I would seriously doubt if any of those gears would fit and work in the Rootes axle, and for the same reason Ford rear gears wont fit in a Chevy rear end. They have no common connections from the drawing board to the final assembled product. The European Capri -Mk I and II - even if the same design as the UK Ford axle will have been machined and built as a metric unit. I know the hardware was all metric. The Pinto, Bobcat. and Mutt II that used the 6.75 inch Ford unit were almost certainly based on the European axle design but probably updated to be machined and assembled with American machines and tooling - that would include part selection for domestic sourcing. The Rootes ring gear I measured is 6.875 inch. Begins with that difference and a dearth of parts support for any of these obsolete designs.

The next issue is the Rootes design utilizes a carrier housing like the US Ford 8 and 9 inch rears that are removable as an assembly from the axle housing. All the Ford axle housings are of the Salisbury design with the gears assembled into the full axle housing and aren't removable without disassembly. It may not make a difference for pinion and ring gear design but probably is a difference factor.

If you want to figure out if any of those gear sets might fit the Rootes carrier, these are the two measurements which must match to within a thousandth or two between Rootes carrier and gear set design. First is the dimension between the pinion centerline and ring gear mounting face on the carrier. The second is the vertical distance between pinion centerline and the centerline of the mounted ring gear. If these two dimensions don't match, the gears will not interchange. IIRC, the Rootes gears are adjusted for mesh with shims, while the Ford axles use a crush sleeve to adjust mesh. As a guess, I think that would require the Ford pinions to be physically longer the the Rootes pinion.

Now that I've rained on your parade, if you can locate a Mk I Capri rear axle from a 2000 (two Liter) it is almost exactly the same size as the Alpine axle, carries a 3.44:1 gear set, has brakes that are almost identical to the Alpine - except Metric, and is the same bolt circle as the Alpine. If you are willing to do the Metal surgery to make it fit, drive shaft, spring pads and shock mounts, that would be a simpler project.

A word of caution though, even going just that low, numerically, with the gearing might cause a condition while driving that you feel the need to frequently drop out of fifth gear because you are down on revs. When the "Dark siders" started using the Rootes rears, most found the 3.89 gears very tractable while driving. My advice is to install hardened keys in your hubs, check the carrier bolts while the axles are out, and drive your Alpine that way until you decide a change is required.

Hope this helps,

Good points I am sure.When I spoke to the owner of trans rebuild shop that ships all over the US he just thoiught that changing the ring and pinion might would give me the desired effect.....not screaming along at 4k rpm at 55mph. The rebuilders do not really do the install so I did take it to local hot rod place and was told that there were no gears available for my car period. ( did i mention that car has V6 mated to a 5spd?). I suppose I could cut out the fenders and install 255.75.18 inchers and accomplish what I need). OK I am just kidding. Had I known this gear changing would be so difficult I certainly would not have purchased the car but I have had a 50 yr Jones for a Tiger but that is out of my price range.

 

[husky drvr]

did i mention that car has V6 mated to a 5spd

OK, given the previous discussion using the online calculator, your engine can't be turning 4000 RPM at 60 MPH in OD. It shouldn't turn that fast in forth gear. Working the math backwards agrees with the calculator.

How long have you had this Alpine? What series is it?

What tachometer do you have installed - original or aftermarket? What ignition system?

You say you have a five speed, the normal is a T5, do you happen to know the build tag number?

What speedometer are you using - original or aftermarket? How is it hooked up to the transmission? Is it a cable or electronically wired?

Have you tried to follow Todd's suggestion about trying to check which set of gears are actually installed?
First thing to do is check the accuracy of your tach - it is 50+ years old and they are known to loose calibration. My tach was reading approx. 500rpm high. Next question: do you have a 4:22 or 3:89 rear? Easy test is to jack 1 rear wheel off the ground and put tape on both the drive shaft and the tire. turn the drive shaft 2 complete revolutions. Your tire should either slightly more (3.89) or slight less (4.22) than 1 revolution. This is important because Rootes had gear sets up to 5.22:1 (Very rare).

Have you tried to contact DanR about this car to see if he can give you any insight about its past?

Any pictures you can post will probably help.

A wild guess is that both your tach and speedometer are off. Finding the cause of both issues may or may not be simple. Almost certainly will involve some detective work. There are different possible solutions, some more involved than others.

Have a good day,

 

[Bill Blue]

OK, given the previous discussion using the online calculator, your engine can't be turning 4000 RPM at 60 MPH in OD. It shouldn't turn that fast in forth gear. Working the math backwards agrees with the calculator.

How long have you had this Alpine? What series is it?

What tachometer do you have installed - original or aftermarket? What ignition system?

You say you have a five speed, the normal is a T5, do you happen to know the build tag number?

What speedometer are you using - original or aftermarket? How is it hooked up to the transmission? Is it a cable or electronically wired?

Have you tried to follow Todd's suggestion about trying to check which set of gears are actually installed?
First thing to do is check the accuracy of your tach - it is 50+ years old and they are known to loose calibration. My tach was reading approx. 500rpm high. Next question: do you have a 4:22 or 3:89 rear? Easy test is to jack 1 rear wheel off the ground and put tape on both the drive shaft and the tire. turn the drive shaft 2 complete revolutions. Your tire should either slightly more (3.89) or slight less (4.22) than 1 revolution. This is important because Rootes had gear sets up to 5.22:1 (Very rare).

Have you tried to contact DanR about this car to see if he can give you any insight about its past?

Any pictures you can post will probably help.

A wild guess is that both your tach and speedometer are off. Finding the cause of both issues may or may not be simple. Almost certainly will involve some detective work. There are different possible solutions, some more involved than others.

Have a good day,

Tach off only 500? Mine was more like 1500 off.
Typical 5 speed and Alpine rear should put you in the 3000 - 3500 rpm range at 70 mph. Most have found this works out great. The engine loves that range, giving good economy and rearing to go when given the signal.

Bill

 

[911tr8r]

Hi
I did connect with Dan but he did not get enuf info in my pics to offer much help. Today I went thru a construction zone where there is radar and it appeared my my car a SeriesV was reading just a few MPH off like 35 and the speedo said 38.
I have had car less than 4 mos. I am excited that it should stop Wed PM. Getting a two res. MC, and proportioning valve and complete flush. Apparently the drums were not working cause tech said fluid to drums was like molasses. I had a 911 event in traffic on way. to shop and had to swerve cause brakes would not stop in time. Hats off to the guy who told me in a previous post to go back to basics. I adjusted the drums but still, did stop, then someone posted about doing a lockup on gravel. Only fronts locked up.
THANKS FOR ALL THE HELP AND PATIENCE. I have built engines (Porsche and small blocks) but it has been 50 yrs since a worked on a Brit sports car. I had Triumphs (rebuilt engine) MGA, MGB and countless limey bikes, in fact today I saw a Royal Enfield. So cool!

 

[911tr8r]

OK, given the previous discussion using the online calculator, your engine can't be turning 4000 RPM at 60 MPH in OD. It shouldn't turn that fast in forth gear. Working the math backwards agrees with the calculator.

How long have you had this Alpine? What series is it?

What tachometer do you have installed - original or aftermarket? What ignition system?

You say you have a five speed, the normal is a T5, do you happen to know the build tag number?

What speedometer are you using - original or aftermarket? How is it hooked up to the transmission? Is it a cable or electronically wired?

Have you tried to follow Todd's suggestion about trying to check which set of gears are actually installed?
First thing to do is check the accuracy of your tach - it is 50+ years old and they are known to loose calibration. My tach was reading approx. 500rpm high. Next question: do you have a 4:22 or 3:89 rear? Easy test is to jack 1 rear wheel off the ground and put tape on both the drive shaft and the tire. turn the drive shaft 2 complete revolutions. Your tire should either slightly more (3.89) or slight less (4.22) than 1 revolution. This is important because Rootes had gear sets up to 5.22:1 (Very rare).

Have you tried to contact DanR about this car to see if he can give you any insight about its past?

Any pictures you can post will probably help.

A wild guess is that both your tach and speedometer are off. Finding the cause of both issues may or may not be simple. Almost certainly will involve some detective work. There are different possible solutions, some more involved than others.

Have a good day,

I was cleaning up shop today and found a new in box old tach and will test against tach in car.

 

[hartmandm]

I have had car less than 4 mos. I am excited that it should stop Wed PM. Getting a two res. MC, and proportioning valve and complete flush. Apparently the drums were not working cause tech said fluid to drums was like molasses. I had a 911 event in traffic on way. to shop and had to swerve cause brakes would not stop in time. Hats off to the guy who told me in a previous post to go back to basics. I adjusted the drums but still, did stop, then someone posted about doing a lockup on gravel. Only fronts locked up.

Have you replaced the rubber hoses in the braking system? If not, start with that. Then push new brake fluid through the system. Start with left front wheel, then right front, then right rear, and then left rear. Then retest brakes. As an initial test, you can elevate the wheel and apply the brakes and try to rotate the elevated tire. At least then you know the wheel cylinders are engaging. Then move on to customizing with new MC and proportioning vale if desired.

Mike

 

[911tr8r]

Lots of work has been done on this 67 SV but some things were ignored...like stoppage. Looking forward to later today when it will stop. Expensive but worth it.

 

[todd reid]

I was cleaning up shop today and found a new in box old tach and will test against tach in car.

Keep in mind that the original tach (and possibly the replacement) are counting ignition pulses. If you have gone from a 4 to a V6 it will read 50% high (3 signals per revolution vs 2) until adjusted.

 

[hartmandm]

Have you replaced the rubber hoses in the braking system? If not, start with that. Then push new brake fluid through the system. Start with left front wheel, then right front, then right rear, and then left rear. Then retest brakes. As an initial test, you can elevate the wheel and apply the brakes and try to rotate the elevated tire. At least then you know the wheel cylinders are engaging. Then move on to customizing with new MC and proportioning vale if desired.

Mike

If the car is a series V and has the stock brakes setup it will only have 3 brake bleed points - left front, right front, and left rear. No bleeder at the right rear.

Mike

 

[DanR]

I had a 911 event in traffic on way. to shop and had to swerve cause brakes would not stop in time.

I had a panic stop a couple of years ago while returning from a British Car Event in Greenville, SC on a heavily travelled 4 lane (I-385) hwy.

Running about 65 with the flow of traffic, a SUV whipped in front on me, rather short , then hitting their brakes for an exit. I was not really caught off guard knowing from past experiences, but I did become frightened that the vehicle behind me would rear end me. Sure was glad the rear disc brakes did their thing. I had to avoid hitting the SUV and the vehicle (s) behind and wrecking. I did run/skid off the highway.

Yes, I am making a pitch for the rear disc. It was designed and fabricated just for this type of situation. Bill Blue ran this type on his Durapine for many years before helping me with mine. Best thing I have ever done to my Blue Boy.

In regads to your type transmission, the pictures you sent were not cler enough to determine what you have. Send better and more detailed for a better answer, or post them here. Another suggestion, if and when you ever remove the transmission from your Alpine, it can then be made certain what it is and what gears you are running.

If you have SV axles your V6 will not cause harm. Make sure the ring bolts are secure and and use hardened keys for the axles. I run a 4:20 gear and do not have any issues at highway speeds running 195 55 15's with my T5 1352-238.

Keep'em-on-the-Road,

 

[Bill Blue]

I not only ran these rear brakes for many years/miles, but am returning to the Saturn caliper because the Miata (circa 2007) calipers/Nissan rotors were too much for my Metric caliper gonzo 11 inch front brakes. It appears the Saturn calipers could be no more perfect for the Alpine if they had been designed for the application. I will be using the Saturn calipers with Nissan Maxima (10 1/2" or so) rotors. Anyone calculating on using a different rear caliper because it is larger (and better), better think some more. Why use a caliper that requires a proportioning valve?
Bill

 

[Barry]

Bill touched on a very important point.

Series Alpines do not need much rear brake force capability because Series Alpines don't have much front brake force capability. The factory 13" steel wheels limit the front rotor diameter to about 10" (9.5" early and 9.85" late) and the front caliper piston diameter to a little over 2" (2.125" for both early and late). Both the rotor diameter and the caliper piston diameter are small by modern standards.

For "road" cars, the rear brakes should be about one-fourth as powerful as the front brakes (aka, 80/20 front/rear) to avoid rear brake lockup during a hard stop on a clean / dry road surface. One-fourth of "not much up front" means that rear disk brakes must have a small rotor diameter and / or a small caliper piston diameter in order to achieve a usable front / rear brake balance. With factory front brakes and 10" rear rotors, 20% rear brake effort would require a rear caliper piston diameter of about 1".

The Saturn rear calipers that Bill likes have a 1" piston diameter. Hmmm?

 

[911tr8r]

stops on a dime now. Dual res. MC for a FOrd Courier and proportioning valve. All new braided brake lines. Pics to follow maybe today but am flying out the door to car show just now. Rear brake lines were shot . When. tried to bleed them mud came out!. MC was a Girling held by one bolt which was not really an MC. Was a slave cylinder. Might as well have hooked a garden hose. Pics to follow. I have owned well over 100 cars and this was the the most mickey mouse. Darned pretty tho. THats what got me. I would have bought it anyway but wish mechanic did PPI would have been more thorough.
Thanks for all the input.

 

[Shannon Boal]

Well, I know Dan's rear brakes are about the best there is. What are the best front brakes?

 

[belmateo]

 

[Shannon Boal]

It would be nice to have brakes comparable to modern cars.....I see upgrade brakes listed for Tigers, but not sure if Alpine V is the same.

 

[belmateo]

I have had good luck with Mustang, Mazda and Jeep calipers. Mounts are easy to fabricate to match rotors of your choosing depending on your application.

 

[alpine_64]

It would be nice to have brakes comparable to modern cars.....I see upgrade brakes listed for Tigers, but not sure if Alpine V is the same.

Alpine and tiger fronts are the same . So the Willowood kits will work... But many require larger wheels.

It's not the disc size that creates the stopping its the pad area and material... And....the grip of the actual tyres

 

[belmateo]

I would be thinking forward and look into an electric parking brake rear caliper as they are becoming more common place now.